This invention relates generally to hydrostatic transmissions and, more particularly, to a cruise control system for use in connection with a hydrostatic transmission.
Hydrostatic transmissions (“HSTs”), including integrated hydrostatic transmissions (“IHTs”), are well known in the art and are more fully described in, among others, U.S. Pat. No. 5,314,387, which is incorporated herein by reference in its entirety. Generally, an HST includes a center section or the like on which is mounted a hydraulic pump and a hydraulic motor. The hydraulic pump and the hydraulic motor each carry a plurality of reciprocating pistons that are in fluid communication through porting formed in the center section. As the hydraulic pump rotates, the pump pistons move axially as they bear against an adjustable swash plate where the angular orientation of the swash plate affects the degree of axial movement of the pump pistons. The movement of the pump pistons forces a hydraulic fluid through the porting to the motor pistons which causes the motor pistons to be forced against a thrust bearing to thereby rotate the hydraulic motor. As the hydraulic motor rotates, hydraulic fluid is returned to the hydraulic pump through the porting. In this manner, the rotation of the hydraulic pump is translated to the hydraulic motor to drive one or more axles of a riding lawn mower, small tractor, or the like.
For maintaining a desired hydrostatically driven vehicle speed, various speed control systems are known in the art. By way of example, speed control systems are disclosed in U.S. Pat. Nos. 4,620,575, 4,553,626,4,281,737, 4,727,710, 5,228,360, and 6,202,779. While such known speed control mechanisms do work for their intended purpose, they do suffer disadvantages related to their size, cost, and complexity. Accordingly, it is an object of the present invention to provide an improved cruise control system.